Ignitor



2 Sheets-Sheet l IGNITOR R. C. MILLIKAN m w m MP w/ ,MM f Am EUma-Seconds /nvenor Roger C, Mf///fan,

by Ma/ fs Afforney.

June 9, 1964 Filed Feb. 1:5, 1961 F ue/ and r, 02I/a/ves Open June 9,1964 R. c. MILLIKAN I 3,136,126

1GN1T0R Filed Feb. 13, 1961 2 sheets-sheet 2 Fig. 4

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Ooooooooooo /nvemon Roger C. M/'l/fkan,

3/ l by ma United States Patent O 3,136,126 IGNITR Roger C. Millikan,Schenectady, N.Y., assigner to General Electric Company, a corporationof New York Filed Feb. 13, 1961, Ser. No. 89,045 8 Claims. (Cl.6t--39.82)

This invention relates to a high altitude repetitive detonator fuelignitor and, more particularly, to a method and apparatus utilizingrepetitive detonations to supply charges of high temperature gas as fuelignition means, and is a continuation-impart of copending applicationSerial No. 666,727, filed June 19, 1957, now abandoned, and assigned tothe same assignee as the present invention.

A repetitive detonator may best be described as an apparatus which burnsfuel in a continual series of detonations to provide a definite supplyof hot gases, and may be gainfully employed, for example, as an ignitorfor initiating further combustion, as a tool for the study of combustionprocesses, or wherever a supply of hot gases may be required. Oneexample of a particular application where the hot gases provided may beemployed to aid or commence a combustion process, is a jet engine mainor afterburner fuel system ignitor or the main fuel system ignitor.

The exhaust stream of a jet engine is generally described as a mass ofturbulent high temperature gases moving through the exhaust at highvelocity. Fuel may be introduced into this stream for further burningand increased thrust, a process which is referred to as afterburning.The turbulence and velocity of the exhaust gas stream is dependent onsuch variables as the rate of fuel consumption, the speed of the jetaircraft, and the altitude of the aircraft. With the stream velocity andturbulence reduced, and with the pressure in the gas stream nearatmospheric, it is apparent that fuel introduced into the exhaust may bereadily ignited by means of a simple spark ignition device such as thewell-known spark plug, and the like. On the other hand, with a jetaircraft iiying at high altitudes and at increased velocity, thecombined elements of the high gas velocity and turbulence, together withthe low atmospheric pressures at such altitudes, lead not only to theloss of flame or flame blowout, but also to extreme difficulty incommencing a flame with a sparkling device such as a spark plug. Thespark obtainable from a spark plug is generally of limited duration andof limited heat release, and the small volume ignition obtained iseasily snuffed or dissipated in the turbulent gas stream. On the otherhand, a repetitive detonator providing a series of charges or volumes ofhigh temperature luminous reacting gas supplies the kind of volume orthermal reaction source necessary not only to initiate but to maintainand disperse the combustion process.

The main combustion chambers of a jet engine receive air from thecompressor. After a high altitude iiame-out, the compressor, underwindmilling conditions, supplies only low pressure, low temperature airto the combustors. These conditions present reignition problems and therepetitive detonator also serves electively as an ignitor for thissystem.

Accordingly, it is an object of this invention to provide an improvedignitor for jet engines, particularly at high altitudes.

It is another object of this invention to provide an improved jet engineignitor in the form of a hot reacting gas generator.

It is yet another object of this invention to provide an afterburnerignitor wherein initial burning takes place in an enclosed area.

It is a still further object of this invention to provide an 3,136,126Patented June 9, 1964 improved ignitor for fuel in jet apparatus underlow pressure, high turbulence conditions.

Briefly described, my invention in one form includes the introduction atpredetermined flows of detonable fuel and oxidizer into the closed endof a combustion tube or chamber having one closed end and one open endwith a critical flow restricting opening forming the open end thereof,which tube is proportioned to promote detonations, and igniting themixture formed thereof at a point removed from the closed end. In thismanner, a first detonation wave is caused to move through the tubetoward the open end of the tube to expel a charge of high temperaturereacting gases from the open end into a turbulent high velocity and/.orlow pressure gas stream containing a combustible mixture and a seconddetonation wave is caused to move through the tube toward the closed endtemporarily restricting further admission of fuel and/or oxidant.

The term critical flow as employed in this specification refers to thatset of conditions of mass iow of a gas through a flow resistor such thatthis How occurs at the sonic velocity of that gas. As will be fullyexplained below, a prerequisite to the practice of this invention is theprovision, in combination with a combustion tube proportioned to promotedetonation burning, of flowrestricting means located at the exit thereofand means for balancing the rate of inflow of gasses into the tubeagainst the predetermined leakage rate through the flow-restrictingmeans whereby this critical liow condition may be created.

These and various other objects, features, and advantages ofthisinvention will be better understood from the following descriptiontaken in connection with the accompanying drawings in which:

FIG. 1 is a schematic representation of one basic form of this inventionemployed as an ignitor;

FIG. 2 is a modification of FIG. 1 adapted as a high altitude ignitor;

FIG. 2a is an enlarged View of the nozzle 22 of FIG. 2.

FIG. 3 is a diagrammatic representation of two cyclic operations of thisinvention;

FIG. 4 shows the basic ignitor of FIG. 2 when employed as a jet engineafterburner ignitor;

FIG. 5 shows the basic ignitor of FIG. 2 coaxially mounted in a fuelinlet of the main fuel system; and

FIG. 6 shows the basic ignitor of FIG. 2 in a combustion chamberseparate from the fuel inlet.

Referring now to FIG. 1, there is illustrated a detonating device orignitor 1 including a combustion tube or chamber 2 with a closed endmixing section 3 and an open end 4. While various types of fuels andmethods of introduction may be employed, one preferred form of thisinvention is disclosed as utilizing C21-I4 (ethylene) as the fuel, andoxygen as the oxidizer, and introducing the ethylene and oxygen ingaseous form separately by means of inlet tubes or feed lines 5 and 6.Inlet tube 5 projects within section 3 and introduces oxygen into theclosed end while inlet tube 6 introduces ethylene into the side ofsection 3 at a point below the projecting tube 5. The particulararrangement of fuel-oxidant delivery as disclosed has been found to givesatisfactory mixing. However, other methods of fuel delivery such asparallel tubes connected to the bottom of section 3, or a single tubesupplying a predetermined mixture of ethylene or oxygen or other fuels,may be utilized with good results.

As the ethylene and oxygen are introduced at a predetermined rate, theresulting mixture flows through combustion tube 2 toward the open end 4.In order to commence combustion of this mixture, an ignition device suchas a spark plug 7 is positioned in the tube 2 adjacent the midpoint ofthe tube length. As the fuel mixture apoxidant'pair and the length anddiameter of the combustion tube. In the iirst instance, it is desirableto employ a quick-burning, high heat release fuel-oxidant combination,characteristics particularly associated with detonable mixtures.Secondly, the combustion tube 2 diamete must be limited in order torestrict the expansion of the burning fuel within detonable limits.Finally, it should be noted that the initial burning of fuel generateswhat is commonly referred to as a combustion wave, which, whileprogressing through the tube, forms a build-up of a high pressure waveimmediately preceding the combustion wave. The high pressure wave formedbecomes closely associated with and a part of the combustion wave, andthe combination is thereafter termed a rdetonation wave. It should beapparent, therefore, that the combustion tube E should be of asuiiicient length to permit formation ofa detonation wave after initialcombustion. The combustion process as described is differentiated fromthe process generally associated with the well known pulse jet engine inthat the pressure ratio across the combustion zone is on the order of:1, while in the pulse jet, this pressure ratio is approximately unity.

The voltage charge to the spark plug 7 is sequentially timed withrespect to the fuel admission to generate a spark after the detonationwave in the inlet section has dissipated and a fresh charge of fuel isintroduced to iiow beyond the spark plug 7 toward open end 4. The devicethen becomes repetitive in the detonation process until voltage to sparkplug 7 'is stopped. Sequential timers such as that illustratedschematically in FIG. 1 (8) are well known in the prior art and merelycomprise means for supplying voltage impulses at regulable intervals oftime. Various other forms of ignition, such as flame and glow plugignitors, as are well known in the art may be employed in place of sparkplug 7. A study of this process as described for the detonator revealsthat oncev each cycle a detonation or shock wave propagates a jet of hotluminous gas which extends two or more inches beyond the tube open end4.

The detonation wave moving toward theVfuel-oxidant inlets may beemployed as a shut-off means. Since neither ethylene nor oxygen willsustain combustion in their individual pure form, the detonation wavewill dissolve in a pressure wave or pulse, moving into the inlets at apressurew hich is higher than the fuel-oxidant inlet pressures and,accordingly, before dissipation, temporarily restricts furtherfuel-oxidant admission to the combustion tube 2. The detonation wavemoving toward and out of open end 4 expels a charge of high temperaturegas from the open end l of the combustion tube 2.

In one preferred form of this invention, a combustion tube 2 having adiameter of 1A inch, and a length of v36 inches, together with anignition device positioned approximately 2/3 the length of thecombustion tube from the open end 4 operates quite satisfactorily asabove described with a mixture of oxygen and ethylene as fuel.

It has been discovered that such repetitive jets of hot reactant gas mayserve as a useful ignition source for jet engines where conditions maybe such that spark ignition of fuel mixtures is diflicult, for example,in the operation of jet engine combustion systems at high altitudeswhere the low ambient pressure and the high degree of turbulence makeordinary spark ignition ineffective. high altitude operation as acombustion system ignitor, the open end 4 of the combustion tube 2 isfitted With an orifice, iiow restrictor, or nozzle 9 to restricttheexiting of the gases and thereby maintain at pressure in the combustiontube 2 greater than the ambient low pressures associated with highaltitudes, and thus contribute tothe For Y 4 etiiciency of the sparkplug operation. The exit area of nozzle 9 must be chosen in relation tothe incoming gas low so as to cause an internal buildup of pressure intube 2 prior to ignition. A more detailed description of the salientfeatures and required operative principles of nozzle 9 in conjunctionwith fuel-oxidant inlet is described in relation to FlG. 2 When anorifice is described as being a critical iiow orifice, this means thatthe orifice is one through which gas liows at sonic velocity when thepressure on the upstream side thereof is at least two (2) times thepressure on the downstream side.

Referring now to FIG. 2, the ignitor assembly l0 includes the basic formof ignitor l as illustrated in FIG. l, together with a modilied form offuel-oxidant and pressure control system. The fuel-oxidant systemincludes a fuel tank ll connected by a fuel delivery line S to the i.Line 5 also includes a pressure regulator l2 next adjacent tank Trl. anda critical flow orifice 13 next adjacent pressure regulator l2. Deliveryof fuel to the ignitor l is controlled by a solenoid valve lid foron-off operation. Similarly, an oxidant tank 15 is connected to ignitorl by means of lineV 6. Line 6 also contains a pressure regulator le nextadjacent oxidant tank l5, a critical iiow orifice 17 next adjacentpressure regulator le and a solenoid valve lf next adjacent criticalflow orifice i7. It is thus understood that a predetermined flow'rate offuel and oxidant is established'at a given pressure. Solenoid valvesltdand i8 may be interconnected in order to be simultaneously operatedby interconnecting means broadly indicated as i9, and solenoid 2u.Solenod valves le and ld are actuated by any suitable timer controlmeans 2l which provides timed operation of fueloxidant delivery togetherwith a spark impulse to spark plug 7l. lt is understood that the timerand power supply 2l may also be employed to provide spark impulse tospark plug 7, or that a separate timer and power supply 3 (FIG. l) maybe employed to provide the spark irnpulse to plug 7. The two timer andpower supplies 2l and 8 are interconnected so as to supply the spark tospark plug 7 in detinite time relationship to the operation of valves leand ln order to maintain proper pressure conditions for high altitudeoperation, ignitor l is equipped with a nozzle 9, FlG. l, or moreparticularly, a flow restrictor or orifice 22. By means of orifice 22 incombination with critical flow orifices 13 and l', pressure in tube 2isY maintained at a predetermined amount regardless of the ambientpressure in the combustion system at various altitudes. An enlarged Viewof oririce 22 is illustrated in FIG. 2a.

An orice type of control rather than an open-close type of valve isnecessary because of the Very high temperature in the ignitor and theneed to avoid quenching the reacting gas. Any blockage of the opening inthe form of an open-closed type valve will not suice because the nozzle,in the first instance, must provide proper ilow of a fuel-oxidantmixture, must be capable of passing high temperature, high velocitygases resulting from detonation in the form of a luminous streamextending into a combustion chamber without quenching and, therefore,must be in effect out of the path of the hot gas stream or otherwise itwill be rendered useless by burn out in a short period of operativetime. In additiomin order to operate the ignitor of this invention as ahigh altitude fuel system ignitor, the pressure in tube Zis critical.The ignitor as described is effectively operated with a nozzle ororifice opening 22 in one end which will under various and varyingaltitude conditions provide the proper pressure rise for effectivedetonation while, at the same time, being also effectively out of thepath of the emitting hot gas stream. Flow conditions must be and arebalanced relative to fuel-oxidant introduction and predetermined leakageout of orifice 2,2.' Orifice 22 is referred to as an open orifice orflow restrictor indicating it is not of the open-closed type.

The particular constructive features and interrelation vof lk to 1, theorifice 5 of pressure rise together with orifice operation in thisinvention are best described in relation to a working embodimentthereof. Tank I1 contains CZH., as a fuel and tank 1S contains oxygen.Pressure regulator 12 limits the C2H4 fuel pressure to about 44 p.s.i.g.and regulator 16 limits the oxidant pressure at about 63 p.s.i.g. Thediameter of the critical flow orifices 13 and 17 are .020 inch and .O32inch, respectively. The diameter of the exit nozzle or orifice 22 is.090 inch. Under these conditions, (22H4 ows into line 5 at 450 cc. persecond, and oxidant into line 6 at 150 cc. per second, to provide astoichiometric mixture. The total flow of 600 cc. per second into theignitor can only be passed out of orifice 22 when the internal pressurein tube 2 is or reaches about 14 p.s.i.a. Although the incoming mixtureis continually leaking from orifice 22, it only does so at a much slowerrate than the incoming mixture. Consequently, the pressure in tube 2rises until the flow from the .090 orice (22) just equals or balancesthe incoming flow from orifices 13 and 17.

The time required to reach this steady pressure depends on the relativeflow rates in and out of the ignitor and also upon volume of the tube.In this instance, the tube length was approximately 43 inches with a 3/8inch O D. and .035 Wall thickness. Volume is 50 cc. With thesedimensions, the time required for steady flow conditions is about .25second.

The exit orifice 22 operates under critical flow conditions (i.e., theflow through it is independent of the pressure outside) for all outsidepressures up to about 1/2 tube pressure. Thus, for the tube described,variation of the outside pressure from about 7 p.s.i.a. to approximately0 can have no effect on its operation. This condition is required for ahigh altitude ignition source. For outside pressures of about 7 to 14p.s.i.a., the only effect on the operation of the ignitor is that thetube 2 ills quicker` FIG. 3 is a schematic illustration of the operatingcycles of this invention, indicating that the apparatus with theforegoing features operates at 2 cycles per second. In reference to FIG.3, it is seen that once each cycle, valves 14 and 18, are opened andfuel and oxidant are delivered to tube 2, which is initially underambient external pressure of less than 5 p.s.i.a., indicating very highaltitude. Pressure is developed because of the balance of flowconditions as described to about 14 p.s.i.a. Valves 14 and 18 areclosed. The mixture is suitably ignited, detonation occurs, and aluminous hot gas stream is ejected from nozzle 22. Thereafter followsthe exhaust period to end one cycle. Variation in orifice sizes andpressures may be varied to provide, for example, 2 to l0 cycles persecond and operation at various internal tube pressures. It isunderstood, however, that there may not be any independent lchange oforifice sizes between orifices 13, 1.7 and 22, because of the necessityof the balance of l flow conditions as described.

It is an important feature of this invention that the ignitor operateseffectively only when detonation occurs and where the balance of flowout of orifice 22, together with iiow in, develops the requiredpressure. l It is quite obvious that under non-detonating combustionconditions, wherethe pressure ratio across the combustion zone is on theorder of unity, very little ame Will be emitting from nozzle 22. ltwill, in effect, be snufed out. With the pressure ratio across thecombustion zone on the order 22 passes, by means of a detonation wave, aluminous hot gas stream.

When the repetitive detonator is employed as a jet engine afterburnerignitor, the tube 2 is not required to be axial but may be in curvedform such as, for example, that shown in FIG. 4. Referring now to FIG.4, there is shown a jet engine exhaust cone 25 having a repetitivedetonator l mounted therein. Detonator l is preferably mounted adjacentor in combination with a flameholder 26 for increased performance, andis the detonator of FIG. 1 or 2 curved to include a first tube section27 parallel to the exhaust cone, a second tube section 28 per- Vfunctionof the distance along 6 pendicular to and entering the exhaust cone anda third tube section 29 directed axially into the gas stream. Fuel issupplied to detonator 1' in the same manner as described for FIGS. l and2. The fuel to be ignited by the detonator 1 is introduced into theexhaust cone 25 by means of fuel nozzles 3i).

Other curved forms may be employed with good results and the particularlocation of the detonator in the exhaust cone may be varied for thedesired operation. Such a detonator supplies charges of high temperatureluminous gas to the exhaust stream for ignition of a combustible fuelmixture therein, and the high temperature gases are advantageouslygenerated independently of the ambient conditions in the exhaust stream.

In FIG. 5, a repetitive detonator 1 is shown as a curved ignitor for themain fuel system of a jetl engine. A casing 31 houses a combustionchamber 32 which is adapted to receive air from a compressor, not shown.Fuel is introduced into the combustion chamber 32 by means of a fuelconduit 33. Detonator 1' is mounted concentrically Within fuel conduit33 over a greater part of its length, and operates in the same manner asdescribed for FIGS. l and 2 to provide a series of charges of hightemperatures luminous gas adjacent the incoming fuel from conduit 33 forignition thereof. In this embodiment, as in FIGS. l and 2, the hightemperature gas is generated independently of conditions existing in thecombustion chamber. This arrangement is further aclvantageous inpermitting the detonator to be cooled by the incoming fuel and in turnaids in vaporizing the fuel. It should also be noted that various curvedforms together 'with other configurations of position for the detonatorinlet may be employed within the scope of this invention. FIG. 6illustrates a conventional mounting of the ignitor l in a combustionchamber 34. lgnitor 1 is mounted in chamber 34 adjacent the fuel inlet3S and arranged to direct the hot gases generated into the incomingfuel. lgnitor 1 may be directed at any desirable angle for optimumperformance. In all cases, however, it is more advantageous to directthe hot gases into the chamber and away from the walls of the chamber inorderl to avoid quenching characteristics or wall effects on the gases.

When certain applications require the detonator to operate over longperiods of time, the high temperatures 'involved may injure or destroythe materials used in combustion tube 2, or, particularly where thecombustion tube is constructed of metal, the high temperatures involvedmay raise the Wall temperature to a point higher than that necessary toinitiate combustion and, accordingly, the detonator will becomeinoperative. Under these conditions, combustion tube 2 may be cooled byvarious air or liquid cooling processes which are well known in the artand necessitate no further amplification.

The invention may also be employed as a tool for the study of combustionprocesses and particularly for the causes and effects of the transitionof a combustion Wave to a detonation wave. The upper section ofapproximately 30 centimeters of the combustion tube 2 may be of glass orother transparent material, or have a transparent aperture therein foruse with a camera. Alternatively, by observing the gas propertiesspectroscopically, as a v the tube, individual parts of the flameacceleration process can be observed. Accordingly, the detonator permitsthe integration of each measurement over many cycles, and thussensitivity may be obtained many times that available in a single Waveprocess.

This invention thus provides an ignitor for jet engines, ram jet, andthe like jet apparatus, which operates on a detonation wave principle toexpel hot gases through a critical orice. When the invention is employedas a jet engine fuel system ignitor, the initiating combustion commencesin an area sheltered from ambient conditions, such as turbulence, andunder sufficient pressure for effective combustion. The stream of hotgases generated may be projected into a combustion chamber Well awayfrom the surrounding walls and ignition of fuel may be commenced throughpurely thermal relationship with the high temperature gases or the hotstream of gases may contain certain additive reaction intermediateswhich may then serve as initiating means for further combustionreactions.

While other modifications of this invention and variations of apparatusthat may be employed within the scope of the invention have not beendescribed, the invention is intended to include all such as may beembraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A repetitive hotreacting gas generator comprising in combination, adetonator chamber closed at one end and open at the other, means tointroduce at a predetermined iiow rate a detonable fuel and an oxidantinto said chamber adjacent the closed end thereof to provide a detonablemixture, critical, ow restrictingmeans at the open end of said chamberto control pressure rise of fueloxidant in said chamber to apredetermined amount Where said restrictor means operating at criticalow velocity passes all the fuel-oxidant flow entering the ignitor at thesame iiow rate as the flow rate of the entering fueloxidant, and meansin said chamber to ignite said mixture to generate detonation waves insaid chamber to expel hot gases through said flow restricting means.

2. A repetitive hot reacting gas generator comprising in combination, adetonator chamber closed at one end and open at the other, critical floworice entry means to introduce a detonable fuel and an oxidant into saidchamber adjacent the closed end thereof at a predetermined rate toprovide a detonable mixture, critical ow restricting exit means at theopen end of said chamber to control pressure rise of fuel-oxidant insaid chamber to about 30 Ap.s.i.a. under which conditions saidrestricting exit means passes all the fuel-oxidant flow entering theignitor, and means in said chamber to ignite said mixture to generatedetonation waves in said chamber to 'expel hot gases throughsaidrestricting exit means.

3. A repetitive hot reacting gas generator comprising in combination, anelongated combustion tube closed at one Vend fand open at the other,means to introduce a pair of separate fuel and oxidant components intosaid tube adjacent the closed end thereof at a predetermined iiow rateand to form a detonable mixture of said components, open critical iiownozzle means the open end of said tube to provide a pressure rise insaid tube above external pressures while at the same time passing allthe fuel-oxidant ow at said flow rate, ignition means to ignite saidmixture and generate detonation Waves in said tube to expel hot gasesthrough said nozzle means and means to repetitively generate saiddetonation waves.

4. A repetitive hot reacting gas generator comprising in combination, anelongated combustion tube closed at one end and open at the other, meansto introduce a pair of separate fuel and oxidant components into saidtube adjacent the closed end thereof, critical flow entry orifice meansconnected to said means to introduce for regulating the rate of flow ofsaid components into said tube, a critical flow exit orifice operativelyrelated to said critical flow entry orifice means to pass all of the Howout of said tube at an internal tube pressure of at least 2 times thepressure external to said tube and sequential timing means to stop theflow of fuel-oxidant into said tube and ignite Vsaid mixture to formdetonation Waves in said tube to expel hot gases through said exitorice.

5. A jet engine combustion system including, a cornbustion chamber,means to introduce air into said combustion chamber, a fuel inlet tubeto introduce fuel into said combustion chamber, and an ignitor for saidfuel coaxially mounted in said fuel inlet tube, said ignitor comprisingan elongated tube closed at one end and open at the other, means toyintroduce a detonable fuel mixture into the closed end of said tube toflow toward the open end at a pressure less than that developed bydetonation in the tube, a critical flow restricting nozzle member at theopen end of said ignition tube to maintain a pressure in said ignitiontube greater than the pressure in said combustion chamber, ignitionmeans adjacent the midpoint of said ignition tube, and means to energizesaid ignition means to generate a pair of oppositely moving detonationwaves in said ignition tube, one of said detonation waves temporarilyrestricting further fuel mixture inlet in said ignition tube, and theother of said waves expelling a charge of high temperature gas from saidignition tube into said combustion chamber coaxially with the fuel fromsaid fuel inlet tube for ignition thereof.

6. The invention as claimed in claim 5 wherein the detonable mixture isa mixture of ethylene and oxygen.

7. A method of igniting a combustible mixture in a combustion chamberwherein a first fuel introduced into a fast moving gas stream withinsaid combustion chamber requires ignition and wherein the method ofigniting is Vconducted in an apparatus comprising in combination anelongated chamber having a relatively small cross-sectional area andhaving one end thereof in flow communication with the fast moving gasstream through a flow-restricting opening, means connected to saidchamber for the introduction therein of a detonable fuel and an oxidantin a manner promoting the mixing thereof and means connected to saidchamber for igniting such mixture on demand, which method comprises:

(a) introducing a detonable fuel and an oxidant to said chamber,

. (b) balancing the total rate of fuel-oxidant introduction against thepredetermined rate of leakage through theiflow-restricting opening tocause the pressure in said chamber to increase to a value at least twicethe pressure outside said chamber whereupon the rate of fuel-oxidantintroduction equals the flow of fuel-oxidant issuing from said oriceindependently of the pressure outside said chamber, and

(c) igniting the fuel-oxidant mixture to generate a detonation Wave toexpel hot gases through the owrestricting opening yinto the fast-movinggasstream to ignite the first fuel therein. 8. A method of igniting acombustible mixture in a combustion chamber substantially as recited inclaim 7 wherein the detonable fuel and oxidant are ethylene and oxygen,respectively.

References Cited in the file of this patent UNITED STATES PATENTS

1. A REPETITIVE HOT REACTING GAS GENERATOR COMPRISING IN COMBINATION, ADETONATOR CHAMBER CLOSED AT ONE END AND OPEN AT THE OTHER, MEANS TOINTRODUCE AT A PREDETERMINED FLOW RATE A DETONABLE FUEL AND AN OXIDANTINTO SAID CHAMBER ADJACENT THE CLOSED END THEREOF TO PROVIDE A DETONABLEMIXTURE, CRITICAL, FLOW RESTRICTING MEANS AT THE OPEN END OF SAIDCHAMBER TO A PREDETERMINED AMOUNT WHERE SAID RESTRICTOR MEANS OPERATINGAT CRITICAL FLOW VELOCITY PASSES ALL THE FUEL-OXIDANT FLOW ENTERING THEIGNITOR AT THE SAME FLOW RATE AS THE FLOW RATE OF THE ENTERINGFUELOXIDANT, AND MEANS INSAID CHAMBER TO IGNITE SAID MIXTURE TO GENERATEDETONATION WAVES IN SAID CHAMBER TO EXPEL HOT GASES THROUGH SAID FLOWRESTRICTING MEANS.